Intel IoT boards generally hover around 10 W at idle. ARM SoMs usually 5 W. You need to order some prototypes for testing of course.

Pricing is quite different from supplier to supplier. Usually around 50 - 100 € Here are a couple suppliers for NXP boards:

Toradex (Switzerland): https://www.toradex.com/

Phytec (Germany / India): https://www.phytec.com/products/

Variscite (Taiwan): https://variscite.com/

Intel boards usually cost around 100 € - 150 €